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How do I remind myself to run in-flight checklists?
When flying a basic light aircraft with no "modern" instrument the pilot needs to remember to do various checks on a regular basis (FREDA every x minutes, change fuel tank every Y minutes etc.).
Just flying the plane can be consuming a lot of attention (especially without auto-pilot or if you become unsure of your position) and it's easy to forget to run those checks. I wouldn't want to forget changing fuel tank so I was wondering:
What are the tools that I can use to make sure that all checks are done on time?

Possible duplicate of How do pilots stay disciplined and use checklists, even after they have become routine?

@Pondlife That one is about "go through your checklist" and pre-flight checks. What I'm asking is for "tricks" to make sure I don't forget to actually run the checks while in flight, when workload and other things can divert your attention.

Ah, OK. I've edited your question to make it a little clearer that you're interested in in-flight checks.

Note: question amended to avoid an "Opinion based etc." closure.

A checklist that includes going through the pre-flight checklist?

I guess I have just been flying too long. I just have chores that I do every five minutes, and I lookup my watch/clock probably two times a minute. So it's pretty hard to miss things. Even when flying an aircraft without an electrical system.
On my knee board I keep a list of things that I have to do in Zulu time, such as reports, fuel changes and things like that.
I don't like relying on smartphones, tablets or specific equipment in the plane with the exception of a timer, which almost every plane has, and a clock. I have a back up to the timer and the clock on my knee board. As of yet the math is still something I can manage.
I encourage you to consider the same, because a reliance an electronic systems will create inconsistencies if you move between different aircraft. On the other hand if you rely on simple timekeeping instruments, which you carry backups for with you on every flight, then you can move from one aircraft to another with confidence that you can still manage the temporal tasks.

In my view, the best tool for reminding yourself of recurring "household chores" is by using a timer, if the noise profile of your aircraft allows it. (Try it! You can probably hear more than you think, even in a loud prop). Either use a kitchen timer (which has a really simple physical interface, although two hands may be required) or your smartphone (a bit more complex interface, typically allows for single hand usage, with the added benefit that you can run multiple independent timers, and that the alarm will not stop sounding until you dismiss it). Modern GA EFIS (for example G1000) typically have timing facilities built in.
If you are unable to use an actual timer, determine the interval of the task (for example every 15 minutes), and use your normal watch. (For example "Check the tank every time the minute-hand passes the 0, 15, 30, 45 marks").

train yourself to look at the watch (wristwatch,cockpit,etc) at least once a minute, just like part of the instrument scan. Pro: It gives you an awareness of the time elapsed, and also helps with lost comms scenarios,etc. Cons: might develop into OCD
pick a visible landmark ahead along your route. "when we pass that large hill, I will check fuel, and contact radar". It works surprisingly well (at least for me), as the brain instinctively/subconsciously  recognizes passing abeam a landmark and raises the alarm on it's own. Pro: easiest to train and execute. Cons: well, you need landmarks
you can use a timer/alarm (wristwatch, phone, tablet). Pro: works every time. Cons: you become reliant on that phone/tablet, and having that alarm going off while on final approach can be annoying
if you use a flightplan with waypoints pick some of them (usually 30-60 mins apart) and circle them with a big red pen. ( if you have the FMS capability draw a circle arround them on the ND and an abeam line).Pro: well, it works. Cons: doesn't work well on VFR flights, since there aren't so many waypoints and they are too far apart.

Every flight has different phases. For example, climbing, enroute, before landing, take off, landing, and others.
When you are in a phase of flight, then you do the chores that you learn to do when you are taking flight lessons. Using a checklist allows you to not forget anything that needs to be done, like lowering the landing gear!


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Is it common for a cold reciprocating engine to stop at idle?
The other day I started the engine of a PA28 and put it at 1200 RPM as per the checklist but the sound didn't seem right - so I tried each magneto and the power dropped a lot on one of them. I then pulled the throttle to idle and the engine stopped. It was on for maybe 30 seconds so it was still cold.
I restarted the engine, went through the standard checklist and everything was fine the second time (I ran the magneto and idle checks once the engine was warm).
Is this behaviour expected from a cold engine (large power drop on single magneto and engine stop at idle)?
For reference, the aircraft is a PA28-180, I believe the engine is a LYCOMING O-360-A4A with ca. 500 hours. The outside temperature was 15C.

I started a cold Cessna 152 yesterday following the POH priming instructions and it started right up, then about 10 seconds later before I did anything, the RPM went up to about 1200 then slowly died down and engine shut off. I then restarted the engine (without priming) and it started right up and the after taxing the run-up before takeoff was normal and I flew for 1.1 hrs without issue. I don't usually hold the behavior of a cold engine against it, but I do listen carefully to what it tells me during the run-up procedure when its warm and immediately before take-off.

What you experienced is common, but it would serve you well to better understand your engine.
There are quite a few engine options for the PA28, so without more specifics I cannot give you specific guidance, but I will address this in a general form.
Spark plugs foul from several different sources.  The leading sources are from excessive unburnt fuel, and from oil.  The unburnt fuel can cause carbon and fuel based buildup on the plugs, or it can come in the form of lead fouling, where lead deposits bridge the spark gap or insulator in the spark plug. Oil fouling tends to happen in higher time engines, but can happen in new engines during their break-in period.  Normally, running at cruise power keeps the plugs clean by scavenging these deposits off.
Again, engines vary, and manufacturer's recommendations vary, but in general, I run with the engine lean during taxi. This reduces buildups and will clear some fouling.  Because the engine running is impacted by engine temperature, I generally do not do a run-up until after taxi, when the engine is warmer.
If an engine is running rough, or the mag check fails, or the engine repeatedly stalls, I will do a clearing run-up, where the engine is run at a higher power setting, typically 1800 to 2000RPM and leaned until it will just continue running. This creates higher temperatures, and tends to burn off oil or other fouling.  This is done for anywhere from 1 minute to about 3 minutes, and then the mixture is enrichened and a normal run-up and mag check are done.
Magnetos do not foul, rather spark plugs foul, and typically the R mag will run the top plugs on one side of the engine, and the L mag will run the top plugs on the other side. Bottom plugs tend to fould more, especially if there is oil fouling. But the point is that whether the L or R mag fails, or runs rough, doesn't tell you exactly what spark plugs it is. A cylinder temp gauge or other instrumentation may, but usually it is determined by disassembling and inspecting the spark plugs.
So to get to the OP question: Large drops at runup are a sign of either a condition which may resolve itself, or conditions which are causing the engine to run less effectively. If they can't be respoved the plane needs to be seen by a mechanic, or someone more familiar with it.  If the mag is rough, and the engine has just been started, then it is premature to perform a normal mag check.  Let the engine ward up more, during taxi, and then check the mags.  The engine should not die at idle.  If that happens repeatedly after the engine is warmer (not even up to operating temps), then there is a problem, and the engine should be checked out by a mechanic or someone with more experience.
In addition to not clue as to what engine you are dealing with, we also don't know the local meteorological conditions. If you are having problems at 0F it is more typical than having problems at 35F.  But in general, engines should not stall at idle even when cold at 40F temperatures.
A final comment. I have trained many CFIs, and I spend quite a bit of time on engines and their operation and work-arounds.  Much of this is not in FAA publications, or even training publications. I find that many CFIs are not a knowledgeable about engine operations and related methods. Being engine smart will help you in your flying, and it will reduce your risk.
Addendum:
As a general rule:  Lycoming: R Mag top left plugs, cyl 2, 4 and bottom right plugs, cyl 1, 3.
Continentals: R Mag fires the top plugs, L Mag fires the bottom. The impulse is the R Mag, as the top plugs tend to get less oil fouling.

Thanks for your answer - additional info: PA28-180, I believe the engine is a LYCOMING O-360-A4A - ca. 500 hours. Outside temp was 15C.

If you have this problem with that engine at similar temps, there is a problem. It could be that the last person flew it full rich, or that it is leaking a little oil.  An OAT of 15C should not cause a rough run or stall after start. When you preflight, look at the oil add history.  With 500 hours the engine is at it's prime, assuming that it was broken in properly, and has not experienced any problems.

One more thing, just to soapbox, when starting that engine, you should use about 1 or 2 shots of prime, at 15C.  At -20C you may need 4 shots. The throttle should be 6 to 12mm open, and should NOT be pumped. If it has to be pumped the primers are clogged, and by pumping the updraft carb, you are introducing the #1 cause of engine start fires.  Depending upon where the plane was initially delivered, it will have either a single primer or four primers.  If you have the time, offer to help a mechanic with oil changes or an annual. Even if you are not mechanical, do grunt work. Great education.

You probably want to add the OAT was 15c and Engine type to the original post to cut down on poor answers. Any properly operating normally aspirated engine should have no trouble at 15c. It's plenty warm enough to maintain atomized fuel.

@mongo I'm guessing here based on my general engine experience... The engine start fire would be caused by flashback of atomized fuel in the throttle body because of the throttle action causing a backfire start condition.

The throttle action per se does not cause a backfire. Rather the backfire is the consequence of the engine not following through on the Otto cycle for one or more cylinders. Ignited fuel then comes out backwards through the carburetor. If there is no excess fuel in the area, it makes noise and the fire dies. If there is excess fuel in the area (collected in the air box and dripping to the ground) that will ignite, and because it is not atomized it will burn slowly. While that happens the carburetor cooks in the flames, and more fuel comes out fueling the situation.

Most recip POHs will have a starting engine fire emergency procedure, which includes continuing to crank the engine for a period of time. That sucks the hot gases. The idea is to contain the fire inside the engine, rather than in the airbox and carburetor.  Good time to re-read your engine starting procedures and emergency procedures.

Modern computerized engines have multiple sensors for air temperature and flow, engine temperature, exhaust temperature and oxygen content that allow the computer to select the optimal fuel-air balance for the engine when started. When you start one of these from cold it's rare for it to run rough. Most airplane engines are manually controlled and carbureted, and it's very normal for them to be a bit lumpy when cold in cold weather, in my personal experience Continental engines are more prone to this than Lycoming. It's less common for a mag to have a big drop, but it does happen when a mag gets fouled and it usually clears itself up. As long as the engine is smooth once heats up you're fine. If you still have a mag drop you can run up the engine and then lean it aggressively to burn off the gunk from the mags.

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What is the difference between a private and a commercial flight according to the US Customs and Border Protection?
From what I understand, whether or not a flight is classified as private or commercial in the eyes of US Customs and Border Protection (CBP) has nothing to do with the Federal Aviation Regulations (FAR) flight rules that they are operating under. For instance, I understand that I can legally be operating under FAR Part 91 and still be a commercial flight in the eyes of CBP. What then is the determining factor?

According to the CBP eAPIS FAQ, this definition is in 19 CFR 122.1:

(d) Commercial aircraft. A “commercial aircraft” is any aircraft
  transporting passengers and/or cargo for some payment or other
  consideration, including money or services rendered.
[...]
(h) Private aircraft. A “private aircraft” is any aircraft engaged in
  a personal or business flight to or from the U.S. which is not:
(1) Carrying passengers and/or cargo for commercial purposes;
(2) Leaving the U.S. carrying neither passengers nor cargo in order to
  lade passengers and/or cargo in a foreign area for commercial
  purposes; or
(3) Returning to the U.S. carrying neither passengers nor cargo in
  ballast after leaving with passengers and/or cargo for commercial
  purposes;

Nice answer! This is good to know.

That's pretty much the FAA definition, is it not?

@MichaelHall Not exactly.  There are some situations where a Part 91 flight can accept money, but still be operating under Part 91 (such as training flights, ferry flights, and other exceptions in 14 CFR 119.1).  In this case, they would still be considered a commercial aircraft by CBP.

@Lnafziger - The OP in the question, Pondlife in his answer, me in my comment, and now you, are all saying the same thing:  If you are receiving compensation it is a commercial flight, regardless of the CFR part you are operating under.  Is there a misunderstanding?  Because I think we all agree...

@MichaelHall Well, I am the OP of the question, but in my comment here I was referring to your comment on this answer which says that it's pretty much the same definition as used by the FAA.  There are differences, which is why I asked the question in the first place (and I pointed out some of them in the previous comment).  There are situations where you can be paid, but still be flying under Part 91 (training, etc.).  Those would be considered commercial flights for CBP purposes though.

@Lnafziger - And my question is that even if you may be operating under part 91, if you are being compensated doesn't the FAA also consider that a commercial operation?  (commercial pilot certificate is a prerequisite for CFI)  I am just not quite understanding whether we even have a disagreement or misunderstanding at this point...

@MichaelHall Okay, I see what you are asking.  It is common for people to think of Part 91 as private and Part 135 as commercial, and I hear a lot of people say something along the lines of "if you are flying under Part 91, then you are a private flight according to CBP."  That was the reason behind my question, as it is clear that there are some operations that are conducted under Part 91 which are still commercial operations.  That's what I was trying to clarify with the question.

@Lnafziger - Got it.  I understand the common thinking, but I have never actually heard anyone assert that as the primary discriminator.  Generally the question of compensation is the first block on the commercial or not flow chart.  To that I have a twist:  What if you are operating under part 135, but are NOT receiving compensation?

@MichaelHall Then by the definition above, it would be considered private by CBP.  That's why it gets confusing for some people, lol.

Well, the Captain is getting paid so it is still commercial.  And I guess you could argue that as an optional FO flying for fun and currency, my compensation is free flight time!  ;)

@MichaelHall Right, hence the question.  CBP says that a commercial aircraft is one that is "transporting passengers and/or cargo for some payment or other consideration."  If it is a 135 trip, but you aren't receiving compensation, then it doesn't meet the definition.

@Lnafziger - You just swung totally the other way on me there...  The part 135 Company I fly with part time is transporting passengers for hire, and is therefore a commercial operation in every sense of the word.  The fact that I receive flight time in lieu of cash as a non-required crewmember would not affect that.

@MichaelHall I agree!  However, CBP would not.  Their definition is different than what the FAA uses (see the answer that we are commenting on).  If the actual flight in question does not have passengers and/or cargo on board for hire (and it doesn't meet any of the other requirements), then it is not a commercial flight per CBP rules/guidelines.  If there are paying customers on board, then it would be a commercial flight per CBP.

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emergency and/or 7700 squawk database or API?
Is there an API or some database somewhere of aircraft that have squawked 7700 (emergency).  Where do mobile apps like FlightRadar24 get their notifications form?
I'd like to monitor when flight to/from/diverted to my local airport are involved in emergencies.

2 problems here. 1) 7700 DB is worlwide, USA, europe, asia or what. 2 second question is another question and is a duplicate. You can get that answer from 'help' section in FlightRadar24 app.

Are you looking to track emergencies or just 7700 squawks?  (If you are talking to ATC and have an emergency you'll just tell them, you wont squawk 7700)

Any flight emergency would be useful to track.  Ultimately I'd like to know when a originating from, arriving at, or diverting to my local airport is involved in an emergency

Flight radar etc directly track ADS-B (as in they have a network of receivers on the ground) or the FAA feed


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Why do airlines have intermediate stopovers with no passenger boarding?
I fly regularly KLM 573 from Amsterdam to Dar es Salaam. This flight does a stop over in Kilimanjaro International Airport and no passengers are boarded, but passengers are disembarked.
There are also other flights of other airlines that I know of that do this (Turkish airlines, Swiss International).
Why is this done? Wouldn't it be more of an advantage to pick up some more passengers in a short intermediate flight in order to maximize profits?
Or does the hassle of loading/unloading luggage and passengers make it less viable?

Hello Fabrizio, thanks for accepting my answer so quickly. Consider to wait a bit longer in the future (e.g. 24h) before accepting an answer to encourage more users to provide their views.

Agree! But that is actually the correct answer! Simple effective and properly written.

@FabrizioMazzoni It's probably correct, yes. But it only says that cabotage is probably the reason: it doesn't give any information that Tanzania actually has cabotage rules. Anyway, if a better answer comes along, you can always change your mind about which answer you accept.

@FabrizioMazzoni you may like to read this whole story..!!!

Related

Wouldn't there also be customs/immigration issues with mixing domestic and international passengers on the same flight?

@DeltaLima: Especially users in different time zones.

DeltaLima is correct but there is a little more to the story which he hints at in his link. This topic is known as Freedoms of the Air. There are five official in total, each dictating in what way an airline may operate in a foreign country. What KLM has done is a:

Normal stop for those getting off.
Technical stop for the onward passengers.

Both are less controversial than what would essentially be letting a foreign operator offer flights in your country, which would not help local carriers ( and which would constitute Cabotage as DeltaLima says).
The technical stop is defined in the second freedom of the air:

Second Freedom of the Air - the right or privilege, in respect of scheduled international air services, granted by one State to another State or States to land in its territory for non-traffic purposes (also known as a Second Freedom Right).

The Third and Fourth Freedom states that the airline can load and unload passengers in a foreign country for transport to and from the carrier home country:

Third Freedom of The Air - the right or privilege, in respect of scheduled international air services, granted by one State to another State to put down, in the territory of the first State, traffic coming from the home State of the carrier (also known as a Third Freedom Right).
Fourth Freedom of The Air - the right or privilege, in respect of scheduled international air services, granted by one State to another State to take on, in the territory of the first State, traffic destined for the home State of the carrier (also known as a Fourth Freedom Right).

(Needless to say, 3 and 4 go hand-in-hand)
Source: ICAO
See also this Boeing document for easier reading.
The other option, aside from not doing it for legal reasons, is that KLM cannot justify the trouble and cost of doing it.

Setting up more domestic presence (websites, additional staff, pricing in regard to competition) in a foreign country is a somewhat complicated business.
There would be additional waiting time on the ground when stuff was loaded and paperwork sorted out.
Furthermore, I imagine that KLM would like to block the free seats for the complete leg as long as possible (which would generate the greatest revenue), so the actual number of available sub-segments for booking would not be that great.

Re your last paragraph, doesn't KLM already have the necessary presence in Tanzania to sell tickets for its international flights?

@DavidRicherby was unclear. they need to work out details and prices a questionable volume of additional bookings possibly with domestic websites (and possibly payment options) to make it feasible. They do not appear to have a desk at Kilimajaro but only a ground handling agent. They have an office in Dar es Salaam.

Could KLM offer the free seats "free" of cost between JRO to DAR, to its former customers, as a way of privilege or promotion?

Very few countries allow foreign operators to provide transport services between destinations within the country.
Since both Kilimanjaro International and Dar es Salaam are in Tanzania, the government will simply not allow KLM to take additional passengers on this flight. Otherwise it would be strong competition for their local transportation companies.
The official word for this is "cabotage":

Cabotage is the transport of goods or passengers between two points in the same country by a vessel or an aircraft registered in another country

(Wikipedia)
Usually these rights are agreed upon in bilateral agreements between countries. Within the EU member states cabotage is allowed and heavily used (e.g. Ryanair) but outside the EU cabotage is rare.

Actually the flight you mention, KL573, is a direct AMS-DAR flight and does not stop in Kilimanjaro (JRO).
Another KLM flight, KL569, does stop in JRO on its way to DAR. It flies the AMS-JRO-DAR-AMS route. You can book this flight from AMS to JRO or from AMS to DAR, but also from JRO to AMS (via DAR) or DAR to AMS. You cannot book the JRO to DAR leg without the continuing leg to Amsterdam.
So there should be people boarding in JRO when you are on your way to DAR. These people will not get off in DAR though, they will continue to AMS.

You may not have seen passengers embark because if they're touring the country they wouldn't go back to JRO to board a connecting flight to DAR, they'd travel overland, making boarding rare -- after all, you've implied that traffic to JRO is mainly tourists, and there's not much incentive for KLM  to push people to do JRO-DAR-AMS instead of DAR-AMS.

How do they keep people from booking the JRO-DAR-AMS leg and then jumping ship at DAR?

I would imagine the fares stop people from doing that.

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How do pilots get enough sleep in preparation for a long night flight?
Are pilots authorised to use sleeping pills to rest before long haul flight that departs at night hours? This question comes in mind as I have flown Turkish Airlines flights that depart at 2.30 at night arriving in the morning with the duration of the flight of about 8 hours. Since the pilot or the co-pilot have to be awake (I suppose, at least one of the 2..) during the flight they will have to get good rest during the day. Sleeping during the day is quite difficult and not natural and this is where my question comes from. If not, what remedies do they use?

I've had sleeping pills in the past, all of them have severe warnings about them affecting your reaction time etc. for sometimes very long periods after using them (in one case 24 hours, iow you weren't allowed to drive or operate machinery at all while taking them).

Short answer: Sleep aids cannot be used this way in the US. FAA regulates the use of such medications with a delay:

Pharmaceuticals (Therapeutic Medications) Sleep Aids:

More on medication advice to medical examiners: Pharmaceuticals (Therapeutic Medications) - Do Not Issue - Do Not Fly.

Only the zaleplon molecule (a Z-drug ⁞ hypnotic) could be used in a practical manner (not publicly available in France nor likely in many other countries).

Circadian rhythm
What you are referring to has got the scientific name of circadian rhythm (circa = around, diēs = day), which is the subject of an article at SkyBrary: Circadian Rhythms. About the night flights:

Night operations create a host of problems for flight crews. The
  primary problem is having to work efficiently and safely at a point in
  time when the work requirements are not in synchrony with circadian
  rhythms. Under worst-case conditions, crew members must perform
  demanding tasks during the early morning hours (2 am to 6 am) when
  their biological functions and performance efficiency are at their
  lowest level. This problem cannot be quickly solved by adaptation of
  the biological clock. Complete adjustment to night work requires at
  least 21 night shifts in a row with no days off. Adjustment of the
  biological clock does not even commence until about 10 days after a
  shift change.

Fatigue
Long article about Fatigue Countermeasures in Aviation, about zaleplon:

This misalignment of the sleep/wake cycle and endogenous circadian
  rhythms could be the result of shift lag, jet lag, or attempting
  sleep at other than the habitual bedtime or at the second circadian
  dip in the afternoon. For such circumstances, the U.S. Air Force and
  Army have approved the limited use of temazepam, zolpidem, and
  zaleplon. These hypnotics can optimize the quality of crew
  rest in circumstances where sleep is possible, but difficult to
  obtain.

Inflight rest
As additional information about sleep management inflight: On a 8-hour flight, usually there will be 3 pilots, and each one will be able to sleep (outside the flight deck).

Air France Inflight rest for crews.
Air Canada When do pilots get to rest during long haul flights?
What Do Cabin Crews' Chillaxation Spots Look Like?

Usually, pilots (and ATC staff) are not allowed to take any sleeping pills during duty. In case they had taken a sleep aid, they are not allowed to perform the (pilot or ATC) duties for a specified time depending on the drug. According to FAA guidance:

Because of the potential for impairment, we require a minimum wait time between the last dose of a sleep aid and performing pilot or ATCS duties. This wait time is based on the pharmacologic elimination half life of the drug (half life is the time it takes to clear half of the absorbed dose from the body). The minimum required wait time after the last dose of a sleep aid is 5-times the maximum elimination half life.

However, the pilots are allowed to use sleep aids occasionally for reasons such as circadian rhythm disruption in commercial air operations provided they don't operate aircraft as noted above.
Pilots use a number of ways to cope of with sleep deprivation, especially in long haul flights.

A number of non-US carriers (like Air Canada, Air New Zealand, British Airways, Emirates, Finnair, Lufthansa, Swiss, Qantas etc) allow in-seat cockpit naps under certain conditions, though FAA has not allowed this still.

Also, ultra-long flights allow for in-flight bunk sleep periods for (both the) pilots.

Aircrew are allowed strict rest periods between flights by regulation.

Pilots alternate flying duties so as to reduce fatigue.

Interesting. Is there a way you could elaborate also on pre-flight? It would make the answer interesting.

@FabrizioMazzoni Are you asking about usage of pills pre-flight?. Its a strict no-no.


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Does the FAA allow a BFR endorsement without a medical?
I am told by a CFI that he can give a BFR but can’t endorse the logbook of someone who does not have a current medical certificate. Do FAA regulations allow a BFR endorsement for someone without medical?

Yes.  Any CFI, who holds a current flight instructor certificate in the appropriate aircraft category and class can give you a flight review and sign off your logbook. That being said, you may not exercise your privileges as pilot in command without a current medical certificate or BasicMed under the conditions specified under §61.23.

Your answer should be YES. Exercising the privileges of your pilot certificate requires you to have a current medical, but flying with an instructor does not require a medical or even a certificate for that matter.

That’s not the issue. The question was whether you had to hold a valid medical in order to have a CFI sign off a flight review in your logbook, which is not required.

The question has been edited so “no“ may have been the answer to the original question. But as currently written, the answer is “yes”; a CFI can sign off on a BFR for someone without a current medical.

It’s edited. Hopefully that makes everybody happy.

There is no such rule. If the CFI themselves does not have a medical or proper endorsements or is otherwise unable to act as pilot in command of the aircraft the flight review will be done in, they might not be able to do the flight portion of the flight review. For instance, a CFI without a tailwheel endorsement is allowed to give a flight review even in a tailwheel aircraft, but since they can not act as PIC, you would need to do so. Which means having a current flight review and a medical. But they can certainly endorse it if it has been done.
Glider/sport/etc pilots don't even require a medical to fly. How does this CFI imagine they get their flight reviews?

Considered narrowly, the CFI’s statement that you relayed is incorrect. FAR 61.56, “Flight review,” does not mention the medical certificate at all, nor does 61.189 (“Flight instructor records”).
Most of the time, “a flight review consists of a minimum of 1 hour of flight training and 1 hour of ground training.” In the case of a pilot who does not have a current flight review and a CFI unwilling to act as pilot in command, they would not be able to complete the flight portion of the flight review, and thus the CFI could not endorse the pilot’s logbook as having “satisfactorily completed the review.”


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Are life jackets mandatory on planes that will never fly over water bodies?
Supposing I'm a regional carrier and my routes never pass over water bodies (sea or lakes which are over a certain size). Am I obliged to carry life jackets on my plane?

No, you aren't.  Flotation devices (i.e. seat-bottom cushions) will do fine. Until they started flying over the Gulf of Mexico to get between Texas and Florida quicker, Southwest Airlines didn't have any lifevests -- just the seatbottom cushions. I don't have the reference for this offhand, so I'll leave this as a comment rather than an answer, but that's the short version.

Even if you don't fly over oceans, most routes fly over rivers. And if the pilot is forced to make an off-airport landing, landing in a river may be very attractive.

Seat bottom cushions would only help on a soft landing

What is the definition of a waterbody in this case?

The answer might depend on which jurisdiction you are asking about. I guess you mean in airspace regulated by the US FAA rather than, say, EASA or other regulators?

Interestingly enough: For US Airways 1549 (2009 Hudson diching), 70% of the passengers did not watch the safety briefing and more than 90% did not read the safety information card. Despite the fact that the flight was flying over the land and life vests were not mandatory, it was equipped for extended water operations. However only 33 passengers out of 150 got their life vest with them when leaving the cabin, and only 4 completed its donning, as visible on the famous image.

highly related: Is there any regulation to ensure that life jackets and safety cards are on-board?

Huffington Post removed the famous image...

Assuming you are asking about civilian flights operated under FAA rules, part 91 rules (14 CFR §91.205(b)(12)) advise that approved and serviceable flotation devices are required to be carried for each occupant during flight where such flight takes place over water outside power-off gliding distance to shore. "Shore" has a specific definition.

If the aircraft is operated [for VFR flight during the day] for hire over water and beyond power-off gliding distance from shore, [it must carry] approved [and serviceable] flotation gear readily available to each occupant and, unless the aircraft is operating under part 121 of this subchapter, at least one pyrotechnic signaling device. As used in this section, “shore” means that area of the land adjacent to the water which is above the high water mark and excludes land areas which are intermittently under water.

These provisions are extended to VFR flight at night and IFR flight in 14 CFR §91.205(c) et seq.
Part 91 subpart F stipulates the requirements for large/turbine-powered multiengine operations (where such rules exclude flights for the purposes of common carriage). In summary, §91.509 requires approved flotation devices when operated more than 50 miles from the nearest shore, and liferafts, survival kits, etc for flights operated more than 30 minutes flying time or more than 100 nautical miles from the nearest shore.
Most "commercial" flights in large aircraft are further regulated in terms of equipment by sections under part 121, part 125, part 135, etc. with similar equipment requirements to those noted above (links take you directly to relevant sections of the code for extended overwater operations under each part).
If operating a commercial air tour compliant with part 136, and such tour is to take place over water beyond minimum gliding distance in a non-compliant aircraft except for the purposes of takeoff and landing, then the code in 14 CFR §136.9 is more strict: occupants must wear life jackets until at least the period when the flight ceases to be over water.

(a) Except as provided in paragraphs (b) or (c) of this section, the operator and pilot in command of commercial air tours over water beyond the shoreline must ensure that each occupant is wearing a life preserver from before takeoff until flight is no longer over water.
(b) The operator and pilot in command of a commercial air tour over water beyond the shoreline must ensure that a life preserver is readily available for its intended use and easily accessible to each occupant if:
(1) The aircraft is equipped with floats; or
(2) The airplane is within power-off gliding distance to the shoreline for the duration of the time that the flight is over water.
(3) The aircraft is a multi engine that can be operated with the critical engine inoperative at a weight that will allow it to climb, at least 50 feet a minute, at an altitude of 1,000 feet above the surface, as provided in the Airplane Flight Manual or the Rotorcraft Flight Manual, as appropriate.
(c) No life preserver is required if the overwater operation is necessary only for takeoff or landing.

In summary, for FAA aircraft operating solely over land, the regulations noted above and by Ralph J's comment proscribe that the required equipment to be carried is minimal.
Of course, what the letter of the law says, and what's a good idea to carry, may in some cases be different things -- I'm thinking here about good practice to carry additional life preserving equipment when operating a GA aircraft for an extended time over water.

My father regularly flies from Missouri to Northern Michigan (lower peninsula). He skirts the South Eastern portion of Lake Michigan. He carries life vests in his Piper, mainly because it helps maintain his relationship with my mother. :)

@CGCampbell your father is a wise man.


text:
How do I achieve a lower stall speed, and capture potential CLmax without enough elevator control authority?
I am running some analysis on a uav, and the results I have found show that with proposed modifications I am unable to trim at my previous $c_{L\:max}$ and thus originally designed stall speed (experimentally determined).  Ideally I want to decrease my stall speed as much as possible (for obvious reasons).  Theoretically with a new flap design I can achieve higher lift coefficients however the elevator does not have enough control authority to obtain steady level flight at these conditions.  Varying my cg location somewhat will allow me to capture my original $c_{L\:max}$ but it doesn't have enough range to reach the new potential $c_{L\:max}$.
What am I over looking that can help me achieve a lower stall speed?  How does the propeller/power, glide slope etc effect this problem?

Just because TRIM doesn't have that much authority shouldn't mean the ELEVATOR doesn't

@PeterKämpf AFAIK it is better to avoid mathjax in the question titles, it slows down the loading of the main page and it looks weird on SEs that do not have mathjax active (if it ends up on the "hot questions" list)

@Federico: Is this compromise acceptable?

@PeterKämpf I turned it into a question, otherwise I thought it was more than fine.

Even if you maintain a force on the stick to stabilize an angle of attack, your pitch moment ($c_M$) will be zero. $c_M$ ≠ 0 means the aircraft will accelerate its pitch rate.

@PeterKämpf, yes {Cm /= 0} means that the aircraft is not in equilibrium, and will pitch down in this instance.  How does the propeller and thrust effect the moment balance?  Could {Cm = 0} be somehow achieved using thrust?  If I am coming in for landing and what to land as slow as possible (ie as close to stall or a factor of safety stall) can I approach this speed because of the glide angle?  I'm not sure if I've clarified my question better or not?  Thanks!

Could {Cm = 0} be somehow achieved using thrust? It all depends on the aircraft in question, see the images in this answer: https://aviation.stackexchange.com/a/9689/1467

It depends, partially on what you precisely mean with "trim".
Pilots use a rather narrow definition where trimming means to zero the control forces for a specific control surface deflection and speed. This is achieved by tabs or springs in the control linkage.
Engineers use it more broadly and include the ability to deflect control surfaces such that the desired attitude can be stabilized. I guess that you refer to this line of thought.
Long before the lift coefficient of a stalling airplane peaks, the flow over part of the wing will start to separate. Ideally it will do so near the trailing edge of the wing root, and the separation will slowly progress forward and outward as angle of attack increases. This separation will shift the local center of pressure back, such that the aircraft will experience an increasing nose-down moment as it approaches stall. To stabilize it at higher angles of attack will, therefore, need nonlinearly increasing elevator deflections. Depending on the position of the center of gravity, the installed elevator authority might not be sufficient to trim the aircraft all the way into the fully developed stall.
If you mean the first interpretation of "trim", then yes, most aircraft will not allow you to zero stick forces into the stationary stall. The trim range should cover the speed for steepest climb, not more. However, if the center of gravity range is wide enough, you should be able to trim an aircraft with rear c.o.g. all the way into the stall. After all, with neutral stability you can ideally trim (second interpretation) any angle of attack with the same elevator deflection angle (note that the nonlinearity explained above will require more negative elevator deflections as you approach stall even in a statically neutral aircraft).
I would rule out that the control forces are too high - after all, when stalling in level flight at 1g the aircraft will fly as slowly as possible, so stick forces should be small.
The effects of thrust depend on the engine installation. With a propeller, more power will add torque and increase the dynamic pressure at the tail. Now it depends whether the prop blast will hit the empennage - if it doesn't, the effect of adding power will at best be be an asymmetric stall.
In case you have a configuration change where the older configuration is known and the new should give the same flight characteristics, use tail volume as a sizing parameter. Horizontal tails of the same volume should give the same control power. Volume is the product of area and the lever arm between tail neutral point and the center of gravity. If the new tail has a different dihedral angle, don't forget to add the cosine of the dihedral angle.
When comparing elevators of the same size but of different flap chords, use the square root of the relative flap chord for comparison. Say the old elevator has a 20% flap and the new one 30%. The new one will have 22.5% more control power for the same deflection ($\sqrt\frac{0.3}{0.2}$).
Depending on elevator chord, at some point more deflection will not help much (typically 20° for a 25% elevator - going higher will add little control power). Now several options can be employed to increase control power:

Change the incidence of the stabilizer. That is what airliners do to compensate the massive trim changes caused by Fowler flaps.
Add leading edge devices on the stabilizer to make the elevator more effective. This adds a lot of complexity for a small gain, however.
Use slotted flaps and double flaps to eke more control power and higher useful deflection angles from an existing elevator. Again, airliners with their wing flaps should point the way.

In damping, both the dihedral angle and the lever arm have a quadratic influence while they have a linear influence on control power. This way one can adjust damping and control characteristics individually.

@spacegirl1923: Don't use the comments but edit the question. You will have more space to work with.

I am using morphing wing technology which makes flap chord comparison problematic at best.  I cannot alter the shape of the body or the root chord location of the horizontal tail either.  However you do make an excellent point with increasing the area of the htail, but currently that is not an option that I am aware of.  (I have a lot of limitations)  I am trying to make sure I did not miss anything in my analysis.  Thanks for your help!

@spacegirl1923: Do you at least have the liberty to relax static stability? With a more aft cg location your necessary trim deflections become smaller. They scale linearly with static stability (= cg location ahead of the aerodynamic center). Thrust won't help, as little is needed during approach and landing.

Yes, see rephrased question above, it allows me to capture my original stall speed, however it doesn't allow me to utilize the potential increase in CL from the flaps.

@spacegirl1923 Sorry, I read the new question only after typing the comment. Can you share planform information? Do you run into maximum effective elevator deflection issues (= more deflection won't help)? It is hard for me to imagine what can be done when I don't know what is available.

@spacegirl1923: I added a section about raising the effectiveness of the elevator, but I have no idea if that is what is holding you back.

Unfortunately some of the most useful information is proprietary however the issue that I am running into is the limitations of the morphing wing technology.  While a direct comparison of a morphed wing control surface to a traditional hinged flap control surface will show significant improvements, I am physically limited on how much deflection I can get (where before I had a range of approximately 25 deg now it's about 10 deg).  From your new section above (thanks btw) I think I will investigate incidence angle, this should allow me to get a larger moment from the elevator, hopefully enough!

@spacegirl1923: OK, now I can start to see your quandary. What about increasing elevator chord? Wing morphing is not so different from a hinged flap, only the sharp bend at the hinge chord is smoothed out. Move the relative chord of the elevator mechanism forward and you can recapture part of the loss. Double the elevator chord will give you 141% effectiveness at the same deflection angle,

I think increasing chord would work however I would have to take that up with the structural team.  I think increasing span would be an easier sell...is there a good rule of thumb for how that would increase effectiveness? For instance can I say that $C_{m,new} = C_{m,old} * \frac{V_{new}}{V_{old}}$

@spacegirl1923: Actually, increasing span is more effective because aspect ratio is increased, and this increases the lift curve slope. For a first estimate the ratio of tail volumes is a safe guess, though. What I meant with increasing chord, however, is to increase the relative chord of the moving part, so the overall planform can remain unchanged. If you add stabilizer trim, you should have sufficient authority without increasing tail volume.

Is wing sweep an option? With inboard flaps and enough sweep, flaps can be moment neutral.
You have inadequate elevator authority to counter the moment generated by flaps. Flaps with a reduced moment require less elevator authority, thus enabling greater deflection and Cl. If inboard flaps are used with a swept wing, they can have reduced moment down to zero added moment when deflected depending on sweep, flap size, span and chord.


text:
Statistics - Does the majority of new pilot training occur at controlled or uncontrolled airports?
Is there any data available on where pilots undertake their training?
I'm interested to know whether most (USA) pilots complete their training at a controlled airport, or at a uncontrolled field.
I'm interested in this because it would likely give an indication of the relative level of comfort of new pilots operating in both controlled and uncontrolled airport environments.
I assume that it's likely that a Designated Pilot Examiner would be more likely to operate out of a controlled field just due to traffic volume, so the location of issuance of a pilot's certificate isn't necessarily a good proxy for where training hours are undertaken.

What is a DPE??

@Terry Designated Pilot Examiner - the guy who does the final check and issues the (interim) pilot certificate. Most pilots do their pilot test with a DPE. https://www.faa.gov/other_visit/aviation_industry/designees_delegations/designee_types/dpe/

I don't think anybody keeps this statistic, but you could search for flight schools and note how many are co-located with controlled fields vs uncontrolled ones. The school I used is at a controlled field, but we often flew to uncontrolled fields to practice, so in reality I think my training was about 50/50 controlled/uncontrolled.

No one really tracks these stats and they would be tough to track on any note. The latter half of my training was out of an uncontrolled field but lots of touch and gos occurred at controlled fields so I had lots of experience talking to the tower even though I was not flying out of a towered field.

I'm interested in this because it would likely give an indication of
  the relative level of comfort of new pilots operating in both
  controlled and uncontrolled airport environments.

As a pilot you are responsible (as per the ACS) for understanding the regulations and procedures for both situations and in todays day and age it would be foolish for an instructor to not at least present both situations in your training. That being said, you can technically get your PPL in an airplane that does not even have a radio but you are still responsible for understanding the regulations and may be asked to explain them on your check ride.

I assume that it's likely that a Designated Pilot Examiner would be
  more likely to operate out of a controlled field just due to traffic

The DPE that I went to was at an uncontrolled field (as are the other 2 in my area). Im not sure this is an accurate generalization.
Keep in mind the DPE will go over your logbook and may look at the airports you landed at. If you dont have sufficient towered experience they may ask extra questions about that but you may not be required to demonstrate it on your check ride.

As Ron stated, I don't think anyone is keeping track of this specific statistic, but given a few factors, such as convenience, cost, insurance requirements, safety, etc., it makes much more sense to do flight training at an uncontrolled airport. I did mine at a towered airport because I had no other choice, but I did all my add-ons (multi and glider) at uncontrolled airports. Besides, a DPE can choose to tell you to fly to any controlled airport near you to find out if you meet the requirements.


text:
Design winglets to counteract tip vortex
I want to know the effect of the wingtip vortex to design a winglet (or a wing horizontal extension) to counteract* this effect.
How could I calculate the momentum produced by the tip vortex, in order to calculate  geometrical characteristics of the winglet to compensate this momentum?
If I knew the velocity of the vortex, how could calculate the produced momentum?
Thank you.

By contrarrest do you mean "counteract?"

Yes, sorry, I mean "compensate","counteract". Thanks.

Possible duplicate of Is a winglet better than an equal span extension?

Please stop following the cult of the wingtip vortex and start to gain a better understanding of the flow around a wing. Stop reading if you encounter any of those myths:

Pressure differences at the tip produce a flow around the tip, starting the vortex. Oversimplification!
The tip vortex causes drag. Wrong!

Unfortunately, the web and much of unscientific literature is full of such myths. Authors with little understanding of the subject copy what they find without considering better sources.
If, however, you find statements like these:

The wing sheds a sheet of vorticity along its span.
The vortex strength behind a wing is proportional to the lift produced and inversely proportional to flight speed.

you have good reason to believe that the author knows his stuff. Read on!
In order to calculate the local flow speed and direction in the vicinity of the wing, all you need is the Biot-Savart law and apply it in a panel code. This calculates the influences of the vorticity on all parts of the wing at a specific location and adds them up.
Here is a list of other answers on Stack Exchange which you might find helpful in gaining a better understanding of aerodynamics and freeing yourself from the wingtip vortex myth:

How does an aircraft form wake turbulence?
Is a winglet better than an equal span extension?
How can I get started on a winglet design?

Wait so wing tip vortex does not cause drag. Then why would you try to reduce it?

I never tried to reduce the wingtip vortex - this is only tried by all those snake oil merchants out there and those who never properly understood what makes an aircraft fly.


text:
Why isn't there a "check engine" light in airplanes?
Why don't small airplanes (like Cessna or Cirrus) have "Check Engine" lights, like cars do?  For the most part, the people flying these airplanes don't know much more about the plane than they do their car.  Wouldn't a "Check Engine" light be useful to many people flying these planes?
Or do the rigorous maintenance schedules required for airplanes invalidate any use that a "Check Engine" light would have?

Don't forget you have manifold pressure, cylinder head temperature, exhaust gas temperature, oil pressure and oil temperature gauges in an airplane while you don't have either in a car.

I'm not a pilot, but I suspect "just knowing something is wrong" isn't going to be useful. With a car, you pull into a mechnanic, or off to the side and call AAA. With a plane you need to know what is wrong now because there is no one look at it until you get on the ground, which you might not be able to do. No one, that is, except Tom Cruise.

aren't check engine lights for ignoring for the next 15,000 miles and saying "I've been meaning to check that out" whenever a passenger brings it up?  Probably I'm just a poor caretaker of my car.

Obligatory Big Bang Theory reference

@coburne If you were a responsible car owner you would learn how to reset the light. ("Fix the problem? I did fix it! The light is out! Everyone's happy!")

@voretaq7, I think he was just making a joke.

@kjmccarx so was I - "Light's out! NO PROBLEM!" (much easier to just reset the thing than the alternate-but-permanent solution of climbing behind the dash and unplugging the lamp!)

The answers seem to miss the obvious point that most GA airplanes were built in a time - 1980s and earlier - when cars didn't have "Check Engine" lights either.

Because there are a whole bunch of them...

With a few exceptions (modern aircraft engines with FADEC systems) a "Check Engine" light on an aircraft would be essentially useless.
In a modern car we have an Engine Control Unit which manages things like mixture and engine timing. The "Check Engine" lamp illuminates when the ECU has detected a fault that requires some sort of attention, but it's not usually specific as to what the fault is or how urgent the problem is.
In most light GA aircraft (like the Cessna or Cirrus in your question) the engines are straight out of the 1950s/1960s: There are no computers managing the engine for you, and the pilot is acting as the ECU.
The pilot should be checking the engine's health regularly (by looking at the engine gauges) and adjusting power, mixture, and propeller pitch as required.
Since there is no computer supervising the operation of the engine in most light GA aircraft there's no system to determine when the light should be on, so there is no "Check Engine" light.

Note that some light aircraft do incorporate warning lights for system status information. For example, the status cluster on newer Piper Warriors:

Top row: Low bus voltage, Pitot Heat off/inop, starter engaged.
Middle row: Vacuum inop, Alternator inop, Oil Pressure.
Bottom row: Not used on this aircraft.
The information provided by these lights is more specific than simply "Check Engine" - directing the pilot's attention to a specific system or condition. The lights are also not a substitute for regularly scanning the engine instruments and managing the powerplant, they're merely a supplement to catch your attention between scans.

I think this answer deserves more upvotes. The Cessna 172R--the first with fuel injection--wasn't released until 1996, if Wikipedia is telling the truth. In most 152s and 172s I've been in, the instrument panels are ancient. Age is the simple explanation here.

This. The engine I fly most is an O-320, first flown in 1953 and preeeetty much not modernized since.

+1 for mentioning an annunciator panel.  I didn't even think about that.

If I owned that Piper Warrior, I would forever regret not buying the model where all of the rows were used. Like when you buy a cheap car, and you can see the spot where the button would be, if only you weren't such a cheapskate.

@MarkHenderson I'm actually not sure any of the PA28s use the bottom row of indicators - I've never seen one where they were used. (Perhaps if you spring for an autopilot in the Archer LX?) They all have the Pitot Heat light that annoys you on VFR days though.

i think its also worth mentioning that planes with a large number of annunciators also have a "master warning" and "master caution" lights in the center of the panel, which, like the "check engine" light have the purpose of drawing the operator's attention to a problem, without stating what the problem is.

Because your basic premise is completely wrong.  The people flying a Cessna or Cirrus generally have a vast amount more knowledge about their planes than the average car owner.  Between the POH (Pilot Operating Handbook) and the general systems information that is part of every level of curriculum that level of knowledge of your average GA pilot is vastly greater than your average driver.
Add to it that indications need to be specific in airplanes.  A pilot needs to know what failed in and what way so they can make an appropriate decision.  Their lives depend on it, unlike in a car.

You say my premise is wrong, but I know the inside of my Jeep's engine better than I know the inside the engine of any of the airplanes I fly.  Sure, I know exactly what to do if my airplane engine fails, by no means does it mean that I have more knowledge of the ( specific engines from the) planes I fly than the cars I drive.

@kjmccarx And you apparently know far more about your Jeep then the "average driver" that John referred to.  Most people are completely oblivious to what makes their car work, whereas the average pilot does know more about the systems than the average driver.

First, consider what a check engine light actually tells you. In short, it could be almost anything, which isn't very useful information. To find out what the specific problem is, you need to go to a garage and have a mechanic run a diagnostic check to determine what triggered the light.
In a car, that's no big deal, but in an aircraft that's a huge problem: imagine that you're flying above cloud at night with potential icing below you and the light comes on (for this discussion, let's leave aside the wisdom of putting yourself in that position in the first place). In the absence of other information, what action do you take? Is it serious enough that you need to get on the ground ASAP and risk the descent through freezing conditions? Or is it reasonable to continue to your destination? Or compromise and look for an alternate that's clear of cloud but not on the way to your destination? The only way to make an informed decision is to have as much specific information as possible, and a single 'something's wrong' light doesn't give you that.
Second, I don't know if your question is deliberately provocative but I question the assumption that light aircraft pilots don't know much about their aircraft systems. Your profile says that you hold a private pilot's license and are in the USA, and the USA FAA's Practical Test Standards require the following:

Task G: Operation of Systems (ASEL and ASES)
References: FAA-H-8083-23, FAA-H-8083-25; POH/AFM.
Objective: To determine that the applicant exhibits satisfactory
  knowledge of the elements related to the operation of  systems on the
  airplane provided for the flight test by  explaining at least three of
  the following systems:

Primary flight controls and trim.
Flaps, leading edge devices, and spoilers.
Water rudders (ASES).
Powerplant and propeller.
Landing gear.
Fuel, oil, and hydraulic.
Electrical.
Avionics.
Pitot-static, vacuum/pressure and associated flight  instruments.
Environmental.
Deicing and anti-icing.

Of course some pilots will cram for their test and then forget a lot of this information, but in general I think it's pretty difficult to get a pilot's license without having a good working knowledge of aircraft systems. Speaking personally, I know a whole lot more about the systems in the aircraft that I fly than I do about the ones in the car I drive (in part because the equivalent instrumentation and information simply aren't available to me in the car).
Finally, maintenance is essential but by itself it doesn't reduce the need for the pilot to understand what's going on. It's commonly said by pilots that it's important to fly the aircraft conservatively for the first few hours after a major service and if you do have some kind of failure in that time then you should suspect it's related to the maintenance. Maintenance can only reduce failures, not prevent them completely, and when something does go wrong then you still need as much information as possible.

Exactly. Just about every pilot I know has participated in the annual inspection of their airplane. I’ve done at least 30. I know where every pulley and turnbuckle is. I look at the alternator belt, brake fluid, spark plug wires, tires, and brakes before every flight. And we have oil temperature and pressure gauges, exhaust gas and cylinder temperature gauges, and fuel totalizers to monitor in flight. I know a whole lot more about my airplanes health than I do about the cars I drive.

First, consider what a check engine light actually tells you. - it tells you precisely what a Master Warning light does, and for the same reason. SOMETHING is wrong, go find it. I'm surprised people are suggesting this isn't a good idea, considering most aircraft (and spacecraft) have one!

Generally, the vigorous maintenance and checks on aircraft mean that a light is superfluous - you'll have checked things fairly recently anyway.
And if you're already in the air and your engine develops a problem, you likely don't need a light to inform you....nor would one particularly help you out, unless the bulb is particularly good at engine-out landings.

I lol'd at "unless the bulb is particularly good at...landings".

Vigorous maintenance and checks are also performed on cars. On-going maintenance for cars includes oil and filter changes, tire pressure monitoring and replacements, brake and rotor inspections, bulbs and lights plus a number of engine related checks and changing parts. Regardless of age, every car needs maintenance. The difference with airplanes is that cars' maintenance isn't thoroughly regulated as airplanes.

It isn't as thoroughly regulated, nor is it as thorough in itself, nor as regularly performed. A car is lucky to get the above once a year, and servicing is usually optional, with road fitness tests only catching things that are already broken....

@Farhan Yes, cars need maintenance. However, as Jon said, they don't usually receive maintenance or inspection nearly as often as an aircraft. Several of the aircraft's systems are literally checked before every single flight, even in general aviation, as part of the pre-flight checks. It's not like we take the engine apart or anything, but there is a pretty significant set of systems checks in the pre-flight checklists, even for very basic single-engine land aircraft.

:"vigorous maintenance and checks on aircraft mean that a light is superfluous - you'll have checked things fairly recently anyway." - I think you have replaced effect with cause. The reason we need all those checks is because the engine doesn't do them itself. This is a problem, not a feature.

The reason the "Check Engine" light, called the Malfunction Indicator Lamp (MIL), exists in cars is due to legislation.  Road vehicles have strict EPA standards to follow regarding emissions that include not only the exhaust and air/fuel mixture, but the fuel tank evaporation, and crankcase oil ventilation. The only way to meet these standards is by computer control of the engine and other aspects of the vehicle.  The light is mandated to indicate when any one of these systems isn't operating within specification, and thus may have higher emissions than what meets the standards.
While drivers think of the light as an early warning indicator for vehicle trouble, the reality is that its primary purpose is to encourage drivers to keep their vehicle within the emissions standards it was originally designed for.  These change over the years, newer cars have more strict standards to follow.
Small aircraft follow the non-road emissions standards, similar to construction equipment, lawnmowers, generators, and off-road vehicles. None of these are required to follow such strict standards (though they must meet minimum standards, and these are getting more involved), and the standards they do follow can be done with no computer control. There is no legislation that requires a lamp indicating that the engine is operating at higher emissions than intended.
Larger aircraft have lower emissions because they are required by customers to be very fuel efficient, and one way to increase fuel efficiency is to add computer control that uses as much energy from the fuel as possible, thus burning it more completely.  These systems are expensive, though, and only make financial sense if the aircraft is going to be flown many, many hours over its lifetime. They also do follow stricter standards, but the indicator lamps and manufacturer diagnostic equipment are more comprehensive for these aircraft to enable overall cost-savings and increased reliability/safety required for passenger service.
The EPA is due to make recommendations in late 2015 and early 2016 that will affect aircraft emissions.  At that point in time it may be that new aircraft will need to be under computer control and will need a check engine lamp.
This might be fundamentally different though.  In a road vehicle if there's a problem, you don't need to know what it is to be safe - you can pull over and call a tow truck.  Aircraft have no such luxury, so while there may be a lamp indicating excessive emissions, chances are good pilots will still rely on multiple other indicators to determine what malfunction has occurred so they can respond best to the circumstances.

Many planes now are being retrofitted with Engine Monitoring Systems, where many things are presented to the pilot and Warnings are presented when limits are exceeded.
This is a JPI Instruments 6-cylinder presentation, my aircraft has the same unit but is only 4 cylinders. The display is customizable for the probes that are installed. There are other manufacturers for monitor systems as well. Most are a big step up from the simple analog meters originally installed. Datalogging also allows data about flights to be downloaded and discussed with a mechanic for troubleshooting, trend analysis, etc.  With Engines costing tens of thousands of dollars to repair, or overhaul, or replace, owners want to keep them running smooth, and get us in the air and back down again safely.

Info:
Engine RPM
Engine Manifold pressure (used to set controllable pitch propeller)
% of engine horse power being created
Outside Air Temperature
Exhaust Gas Temperatures/cylinder (used for leaning out the mixture as one climbs)
Cylinder Head Temperatures (used to let you know if a cylinder is running too hot, or colder than the rest, both indicative of a problem)
System voltage
Amperage flow
Oil Pressure
Oil Temperature
Fuel Pressure
Fuel tank levels
Total fuel
Fuel flow (gallons/hr)
Fuel Used
Fuel Remaining
Time to Empty
Carburator Throat Temperature (carburated engine)
Additionally, it can send data to a moving map GPS to show a fuel range circle

The "check engine" light on a car is triggered by the on-board diagnostics computer that most every (if not every) car manufactured since 1997 has been required to have (if it is to meet U.S. standards, anyway).
On the other hand, small airplane engines, due to the very conservative nature of aviation, the cost of certification (even just certifying a change to an existing design), and concerns about reliability and redundancy, are almost unchanged since the '50s (no on-board computer, for example).  Fuel-injected engines, I believe, are all mechanically operated, rather than electronic like you would have in your car.  Without an on-board computer or electronics, there is nothing to trigger the warning lights that we've taken for granted for the last twenty years in our cars*.
*Many small airplane engines do have at least a couple of warning lights, such as low-voltage, low oil pressure, etc., but they are controlled by simple relays rather than by a computer.
Source: I'm a flight instructor, and flew an "amateur-built experimental" airplane for a few years.

Modern aircraft generally have a "master warning" and "master caution" warning lights which direct the pilot to scan the panel to identify the failed system. Master Warnings impact directly on the safety of flight, master cautions are the "need to know about but don't panic yet" systems, eg, an engine fire is a master warning (yes, there's lots of other alarms going off for this as well), but an oil pressure drifting outside of it's normal operating range or a diminishing hydraulic quantity would only trigger the master caution.

The approach taken in designing aircraft, and certifying their equipment, is to provide for the greatest reliability at the cost of increase pilot workload. The pilot mostly has very little to do for a majority of the flight, being cruise-at-altitude, so it makes sense to require the pilot to scan and interpret simple, reliable indications of current engine status, and draw inferences as to the operational health of the engine as a whole.
For example, the process by which fuel and air is mixed in the carburetor of a non-turbine engine is completely a manually-controlled process. The human is involved as the feedback control element in a closed-loop system, where the mixture control (lean to rich) is the effector, and the RPM and altitude gauges, or the Exhaust Gas Temperature gauge (EGT) are the affectors. The pilot adjusts the mixture to the point which peaks EGT or RPM, and perhaps makes a small adjustment "in the rich direction for cooling", but this is done during climb and descent, as the altitude is changing, and is completely initiated by the pilot (frequently prompted by an item on a climb or cruise flight phase checklist).
Why not delegate this task to an automatic system? Well, first of all, that would provide another point of failure. The EGT and RPM indicators are quite robust and unlikely to fail; likewise with the mixture adjustment knob/lever. The pilot provides the "complex" control system closed-loop control. Imagine if the controller of an automatic system were to fail, and the engine remained in its leanest setting during descent? The system could go into pre-ignition or worse, pre-detonation, leading to a catastrophic failure of the engine! No, the FAA and aircraft builders err on the side of fewer automatic systems in favor of simplicity and reliability.
Someday ask a pilot about all the various things they must tend to, which could be attended to by a modern, computer controlled automatic system. You'll be surprised!

We must make light aircraft more idiot-proof, so we can have more idiots flying light aircraft! Oh, wait... :-)

authors: Bob Jarvis - Слава Україні


text:
How do airlines ensure each passenger has a life jacket before a flight?
It's very easy for a passenger to walk away with a life jacket. What do airlines do in general to ensure that there is a life jacket available for each passenger? Do they check it manually as part of pre-flight check up?

It's been quite a while since I last flew internationally, but US domestic flights use the seat cushion as a "flotation device". I'm not sure how easy it would be to walk off the plane with a seat cushion tucked under your arm without being noticed, and it would be pretty obvious to cabin & cleaning crews that one was missing afterward.

I'm specifically asking about life jackets and not seat cushions, which you have rightly pointed, is difficult for a passenger to walk away with.

Difficult ? Just put it in your suitcase!

I always feel for it under my seat during the safety briefing.  If it was missing, I would bring it to the attention of the cabin crew.

Possible duplicate of Is there any regulation to ensure that life jackets and safety cards are on-board?

not a duplicate: this question asks how the regulation is actuated, point not addressed in the presumed duplicate.

It's essentially a manual check for many airlines, performed as part of the pre-flight checks.
However, the airline I have worked for recently upgraded from manual checks to RFID tags on each lifejacket (a sticky tag kind of like this). The RFID tags can be read from the aisle by a handheld reader. So the person who does the checks simply walks down the aisle with the reader and is able to tell if a seat is missing a jacket and also if the jacket needs to be replaced due to the expiry date fast approaching.
In addition to a tag on the actual life jacket there are also security RFID tags across the life jacket holster under the seat. So the scanner is able to tell if the life jacket has been tampered with as the security tag would have been broken.
As for the frequency of checks, different regions have different requirements. Usually life jackets are only needed at all if flying over a large body of water. I believe the USA requires a check before any flight which passes over the USA (as well as water). Europe requires less frequent checks.

I'm not quite sure life jacket is compulsory for each flight. Of course it is for flight passing over an ocean, but not necessarily all other flights. Thus, checks may not be needed before any flight which passes over the USA.

True, I overlooked that. I've updated my answer. Thanks.

Yes. It is part of the pre-flight check of the cabin crew to check for the availability of life jacket under each seat.

But do they actually check? Or is it just part of the procedure and a tick-box?

@Richard I've never met a pilot / flight crew who didn't perform pre-flight "to the T" before every flight. I'm sure there are some, but the consequences of "just ticking the box" are literally life-and-death for almost every tick-box.

@Dan - A quick google would suggest that it's relatively common to find one missing.

@Richard as I said in my answer not every region (e.g. Europe) requires a life jacket check for every single flight but rather, say, once a week (or less frequent). I guess this is due to the large amount of time needed to do a thorough check. Therefore if some numbnut takes one as a souvenir it might not be caught until later.


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Why do we need DME or RNAV when using VOR navigation above FL240?
According to FAR 91.205(e) there must be DME or RNAV system when a pilot uses VOR navigation above FL240. However, why does the regulation say we need it from FL240, not from FL180 where class A begins?

The consensus of internet wisdom seems to be that no one knows for sure, but the most likely explanation is that before class A existed there was Positive Control Airspace (PCA) that started at FL240, and DME was a requirement in PCA. The main reasons for requiring DME were:

There's a limited number of high-altitude VORs so it isn't easy to use cross-radials from other VORs for fixes or position reporting; DME is a simple alternative
If there's no radar coverage then ATC can still manage lateral separation effectively using DME

That all seems plausible enough, but some sources out there say that PCA started at FL180, not FL240, e.g. this FAA history document:

[VFR on top] was a principle [sic] factor in the [Grand Canyon] crash and led to
  "Positive Control Airspace" (PCA) FL180 and above. Because of the
  speeds of the aircraft involved, non-radar procedures were unwieldy
  (standards called for ten minutes between aircraft; some 80 miles for
  a typical jet), even with the development of aircraft installed
  Distance Measuring Equipment (DME) and the reduced separation
  available between DME equipped aircraft (20 miles).

FL240 is also where ATC starts using Mach numbers instead of knots (ATC orders section 5-7-1(f)) and the separation minima change (section 8-4-4). I don't know if that's for historical reasons or physical/operational reasons, but it looks to me like FL240 is considered the general starting point for high-altitude operations (14 CFR 61.31 requires a high-altitude endorsement for aircraft that can operate above 25,000' MSL).

I would add that in a non-radar environment, having the precision of DME would allow better position reporting over lower precision cross-radials; this would be especially important at the higher speeds of aircraft most likely to be at those higher altitudes.


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Why is there no 100% power in the POH power setting table?
I've flown a piper cadet arrow. The airplane has an engine of 200 horsepower at 2700 RPM. According to the power setting table in the POH, the maximum power we can set is 75% horsepower. With 100% power, we could fly faster (more fuel would burn though). Why doesn't the manufacturer provide the 100% power setting?

If you fly in ground effect the whole way to your destination, you can theoretically cruise at 100% power.

There are no 100% power setting tables because it is impossible to cruise at 100% power with a normally aspirated engine.
100% power is rarely available, even at takeoff.
It is only available at sea level when the temperature is 15C and the altimeter setting is 29.92".

Okay, I've got this figured out. What we do is start a commuter airline running back and forth from a strip at the south end of the Dead Sea to one at the north end. We operate only at night, and we fly at full throttle at sea level. It's about a 30 mile flight. If the temp and altimeter are such that we're not quite getting 100%, we can drop to -400 MSL and still be 1000 AGL (or should we say AWL?).

100% power on a typical aircraft engine is only good for short durations like takeoff or emergency maneuvers. Sustained 100% power setting will destroy the engine.
Not to mention flying faster is not always a good thing. It means higher aerodynamic loads on the airplane. Especially when you hit some turbulence.

There was a down vote. I canceled it with an up vote for the simple reason that this post answers most directly, in my opinion, the question. It would make no sense to have a 100% cruise entry (forgetting that you can't really get that), when doing so would destroy the engine.

@Terry Is that true, though? I don't have a list of engines in operation by model, but the top two manufactured GA aircraft (C-172, PA-28) use a Lycoming O/IO-360, which doesn't have a max continuous power, just a rated horsepower.

Destroying an engine and adding unnecessary wear and tear for a negligible performance benefit aren't the same thing.  Also, we need to be careful not to confuse 100% power with 100% throttle which could confuse those who aren't familiar with the differences.

@Nathan What I probably should have said (in line with MortensenAviation's comment) is something like running an engine at 100% power continuously will greatly reduce it's life and significantly increase the possibility of an engine failure. That said, I'm not a powerplant engineer, but as a child growing up at airports and then later as a GA pilot then airline pilot, the accepted wisdom was that reciprocating aircraft engines are typically not designed to run at 100% power continuously. The primary problem, as I understand it, is heat.

authors: المرادي المرادي


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Which en-route services are available to UK GA pilots?
I have recently taken up flying again in the UK, and although very little has changed in the 10 years I have been inactive, the one area which seems to have changed is in the en-route services available to pilots.
It used to be the case that you could request a Flight Information Service (FIS) and a Radar advisory (RA) service - I seem to recall there being one other which I never used, which I cannot quite remember the name of.
I believe the FIS is now referred to as a "Basic" service, is this assumption correct? Does it vary in any material way from the defunct FIS?
What other services are available to GA pilots in uncontrolled airspace? Where do I find the details of stations and what service(s) they provide?

Some information here: Services are Basic Service, Traffic Service, Deconfliction Service, Procedural Service. Also this flyer.

Thanks @mins - If nobody feels llike writing up a good answer I'll do so from the official sources when I get time. I think this is a useful Q/A to have here at aviation.se

According to UK AIP ENR 1.1 "General Rules", chapter 2 "UK Flight Information Services" the UK FIRs meet the ICAO requirements with the following Flight Information Services (FIS): Basic Service, Traffic Service, Deconfliction Service and Procedural Service.
This is an extract of the contents of the chapter:

Basic Service
  Provides advice and information useful for the safe and efficient conduct of flights. This may include weather
  information, changes of serviceability of facilities, conditions at aerodromes, general airspace activity information, and any other
  information likely to affect safety. The avoidance of other traffic is solely the pilot's responsibility.
Basic Service is available under IFR outside controlled airspace in any meteorological conditions, or under VFR. A pilot may change
  heading, route, or level without advising the controller. A controller will not issue specific heading instructions; however, generic
  navigational assistance may be provided on request.
Traffic Service
  Traffic Service is a surveillance based ATS, where in addition to the provisions of a Basic Service, the controller provides specific
  surveillance derived traffic information to assist the pilot in avoiding other traffic. The avoidance of other traffic is solely the pilot's
  responsibility.
  Traffic Service is available under IFR outside controlled airspace in any meteorological conditions, or under VFR.
Deconfliction Service
  A Deconfliction Service is a surveillance based ATS where, in addition to the provisions of a Basic Service, the controller provides
  specific surveillance derived traffic information and deconfliction advice.
  A Deconfliction Service shall only be provided to flights under IFR in Class G Airspace, irrespective of meteorological conditions.[...] A controller will provide traffic information, accompanied with a heading and/or level aimed at achieving a planned deconfliction minima.
Procedural Service
  A Procedural Service is a non surveillance ATS where, in addition to the provisions of a Basic Service, the controller provides
  instructions, which if complied with, shall achieve deconfliction minima against other aircraft participating in the Procedural
  Service. Neither traffic information nor deconfliction advice can be passed with respect to unknown traffic. A Procedural Service shall only be provided to flights under IFR, irrespective of meteorological conditions. [...] the pilot remains wholly responsible for terrain clearance at all times. [...] A controller will provide deconfliction instructions by allocating levels, radials, tracks, routes, time restrictions, approach clearances and holding instructions, or use pilot position reports, aimed at achieving a planned deconfliction minima.


text:
How are airspace violations detected?
Are airspace violations (e.g. entry to class B without clearance) based on primary radar and/or Mode C transponder, or something else?
I read that Mode C altitude is based on pressure altitude, i.e., set to 29.92" ... but presumably that's adjusted at the ATC facility based on the current pressure before being used for altitude enforcement.
This begs the question, what would stop one (hypothetically), just winding back the altimeter pressure reading to appear to be at a lower altitude?
So to summarize: How are airspace violations detected:

What data input is used?
If Mode C reading is used, is it based
on pilot's altimeter?
Would winding back the altimeter make a
plane report a lower altitude?

I busted class D one time by about 0.3 to 0.5 miles and they did not really care.

@SpongeBob I probably have too... I'm more concerned with busting class B without a clearance.

The transponder usually uses its own pressure reading, not what is set in the pilot's altimeter. So to prevent cheating as you describe, it is inspected and calibrated every 24 months. Tampering with it would be difficult to do on the fly because you'd have to adjust it based on the current atmospheric conditions and what altitude you want to seem to fly at. But yes, you could, in theory, adjust its readings to broadcast something different.
As far as I'm aware, only major violations are really pursued, or if ATC knows who you are when you commit the violation.

Yes, I saw this about the aftermath: http://aviation.stackexchange.com/questions/9/i-just-flew-into-class-b-airspace-without-a-clearance-now-what

Does this mean that primary radar is used for, say Class D (and perhaps C) airspace, which, in the U.S., a Mode C transponder isn't required for?

@CJBS I'm not sure what you mean, related to the topic. A lot of Class D's don't even have radar, or they might only be tied in to the radar of a nearby class C.

If you really screwed up (like "cut through the heart of the New York Class B airspace squawking VFR and not talking to anybody") ATC will probably follow you on their scope, determine where you're landing, and you'll receive "the dreaded phone number" to call when you land (either from local ATC, or they'll call the uncontrolled field you landed and ask "Who was that plane that landed at your field at 1320 Zulu?")

@StallSpin - I was implying that, for such fields (Class D or C airspace), if there's no primary radar, and/or an aircraft doesn't have altimeter reporting equipment, then it's not possible to track violations of such airspace.

@CJBS That's correct, as far as I am aware.

@CJBS An eagle-eyed tower controller who knows their airspace and local landmarks could probably issue violations visually, but I doubt that's common practice (again, unless the pilot really screws up and is doing something like overflying a class D airport at 1500 feet directly over the field not talking to anyone) If you're close enough that they can read your N number without binoculars and you're not talking to them there might be something said :)

@voretaq7 - Laterally, this is probably true, but vertically (unless a gross violation, like you mention), this would be difficult. Vertical boundaries change as the pressure changes, and there are few reference points in the air.

@CJBS Airspace doesn't change with air pressure... You adjust the altimeter for pressure variations so that it reads the correct altitude. The only airspace that can change with pressure is Class A, but they don't assign aircraft to the couple-thousand feet in conflict.

@StallSpin - You're absolutely right. I'm mistaken - thanks for the correction. I suppose it comes down to how often altimeter variations are updated (e.g. METAR) by the tower, but even then, it's probably not significant. Still difficult to judge how high something is accurately though.

@StallSpin they won't assign  FL180 when the altimeter is below 29.92, but they can when its above

In the event of a disagreement between the transponder altitude and the pilot's stated altitude ATC is required to go with what you tell them on the radio. So if their screen says you are at 18,000 but you say "no, I'm at 15,000" they go with that number. Therefore, if you do fudge your numbers a bit for whatever reason, ATC will be unable to do anything about it. They will also not issue avoidance vectors to the A340 approaching head-on at 0.8mach - you are, after all, 3000 feet lower than the Airbus.
Regarding the "dreaded phone number to call" - once you have landed and parked you are no longer air traffic and no longer required to follow their instructions. In many cases the FAA cannot issue you a violation without your co-operation, so don't give them any.

FAR 91.217 deals with discrepancies http://www.ecfr.gov/cgi-bin/text-idx?node=14:2.0.1.3.10#se14.2.91_1217


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What are the properties of the wing (airfoil symmetry, angle of incidence) of an aerobatic aircraft?
On an aerobatic aircraft, such as an Sbach342, what type of airfoil does it have and what angle of incidence does it have in relation to the fuselage?

There are a few things to consider for a good aerobatic airfoil. The transition between attached and separated airflow has a big influence for spins or snap rolls, and a good aerobatic airfoil needs only a small change in AoA (angle of attack) to fully transition between the two. To achieve this, it helps to shape the forward part similar to an ellipse (a lemniscatic function, to be precise), and to use a nearly straight line for the last 70% of chord. The goal is to have a Stratford pressure rise on those 70% which gives the maximum possible pressure gradient without separation. Increase AoA just a little, and you have fully separated flow over those 70%.
When all works as planned, you can get the plane out of a spin by applying rudder at, say, 45° before the fuselage points in the desired direction and get out of the spin within 10° of that direction. Same goes for snap rolls, they get really snappy. It is a real pleasure to fly such planes, but you need some discipline. There are no aerodynamic warnings before you stall, and stalling comes immediately. On the other side, with the limited lift loss of such an airfoil and the powerful engines of aerobatic airplanes, stalling is no big issue.
A major reason for mounting the wing at 0° incidence is that you need little elevator correction in a roll. Rolling happens about the longitudinal axis of inertia, and if the wing is aligned with this axis, it has 0° AoA at 90° and 270° of the roll and at 180° the inverse of the AoA it had in level flight. With a symmetrical airfoil, lift is always correct, and if the aircraft flies at zero stability, you need not to move the elevator.
Mistimed elevator movement in rolls leads to immediate changes in flight path direction (happens really easily, and is easy to observe from the ground), and it is very hard to pitch the whole airplane just at the right time so it has no lift (read: side force) in knife edge flight, but the right lift in inverted flight. Just for flying inverted, many regular airfoils are just fine, but it is in the transitions where the symmetric airfoil has a clear advantage. A fast roll with a cambered airfoil will result in a corkscrew-shaped flight path because you cannot pitch quickly, let alone precisely, enough.

Thanks for explaining the relation between the rigging of the wing, the longitudinal axis of inertia and the symmetry of the airfoil. I never thought of it that it way, but it really makes sense. Great answer!

I did my first roll in a Grob Twin Astir, a glider. There, you need first to pitch up, then stop the pitching motion. Then you can initiate the roll, but if you don't pitch down during the knife edge portion, the plane will change direction. Inverted, you need to keep the nose up, and so on. After my first roll, I was almost 90° off course. That makes you realize how important the elevator is in an unsymmetrical configuration.

Most of these aircraft, like the Extra 300, will have symmetrical airfoils at 0 angle of incidence. As DeltaLima pointed out, the angle of incidence is the angle of the chord line of the airfoil versus the longitudinal axis of the aircraft. Angle of attack is the angle of the airflow versus the chord line of the airfoil, which of course changes with flight conditions.
A symmetrical airfoil allows the wing to perform just as well upside down as right side up. An angle of incidence of 0 degrees helps the plane as a whole to perform in a similar way.
You will probably not find many specifics about the airfoil design, as these are specialized aircraft and airfoil design is generally a proprietary subject. However, you can look at symmetric airfoils in places like the UIUC Airfoil Database.

You are quite right: Its specification doesn't tell any details about what is asked for :-(


text:
Can a commercial cargo aircraft be converted into a commercial passenger aircraft, and vice versa?
Just saw a video in a news, a military cargo plane carrying people stranded in some country. The seats were like in a commercial airliner. This led me to ask the question.
Would it be possible to see some examples where it was done, along with the procedure?

This paper details the general procedure for a "dedicated passenger" to "dedicated freighter" conversion.  http://www.icas.org/ICAS_ARCHIVE/ICAS2014/data/papers/2014_0001_paper.pdf

There are such a thing as "Quick Change" aircraft, allowing entire 'pallets' of chairs to be exchanged for cargo.
Image courtesy of canalblog.com
Image courtesy of airliner.net
Nice film to show the process.
Military transport aircraft can also be fitted out with stretchers or seats, or whatever other combo of stuff you want. To the best of my understanding these lock in like any other cargo pallet in the floor. They are less concerned with aesthetics and more with practicality:
Image courtesy the DOD via Wikimedia
Image courtesy of aarcorp.com

It should be noted, that for military it's the standard way of doing things. Air forces generally don't have dedicated planes for carrying people, so whenever they need to move troops, and they do often, they always use these removable seats (unless they charter civilian plane).

Excellent explanation and illustration

I am missing a source stating how many of these Quick-Change aircraft are available at different fleet operators. I doubt that FedEx could convert any single of its planes, but that's just a gut feeling...

@Alexander few quick-change planes exist, mostly because I think it's difficult to get an efficient mixed service. Pemco states that you can only get in 8 instead of 9 pallets and it takes 20-30 minutes to get the seats in and out. I can't find any number built either....

@Alexander : But Fed-Ex planes don't have windows. Or do they?

@Firee They would never have interest in going into passenger ops for starters. The side windows are plugged or they are dedicated freighters without them at all...

The commercial type is called a combi aircraft.

...and sooner or later the seats are all located at the wrong airport!

It should be noted that the military aircraft pictured has fold-out seats along the sides. Those seats are most likely permanent, while the ones in the middle are just ordinary freight.

@fooot: No, a quick-change is an airplane that can carry passengers or freight.  A combi carries passengers and freight.

It applies to helicopters too.
When on holiday in the West Indies, one of the locations offered helicopter rides.  If anyone booked one, they contacted the local freight helicopter company who put the seats back into the helicopter, then they flew you round the bay, then took the seats out again to continue their bread-and-butter freight work.
The pilot told us helicopters come with seats, they took them out and put them in the shed.  They formed the company to shift building materials to construction sites.  One day a man approached them and asked if they could do sight-seeing rides for tourists.  They checked the seats were still in the shed and said "of course".

I used to fly a Twin Otter aircraft that was used in the UK to carry cargo (newspapers) at night and passengers in the day. The seats were carried in the rear of the aircraft and the pilot who flew it at night put the seats in before he went home. No certification was needed as there were no modifications.

Yes. But with any modifications, the airplane will need to get re-certified by the authorities (FAA in the US) and approved, because it would have sustained modification to its structure.

This is only for massive total conversion from a dedicated commercial passenger configuration to dedicated freighter configuration - one where doors are changed, flight controls and electronics moved/reprogrammed, major interior restructuring is undertaken, etc.  For craft that are dual-purpose with simple removable seats (quick change) there is no need to re-certify.

Good points by both of you